Xenon gas is a very attractive anesthetic agent because of its minimal effects on the cardiovascular system, lack of metabolism, and rapid induction and emergence. However, xenon is used only rarely because of its high cost compared to common inhaled anesthetic agents. The long- term objective of this application is to make xenon anesthesia available for widespread use at low cost. The specific aim is to develop a practical ventilator for xenon anesthesia that operates in a closed-circuit, rebreathing mode to minimize the loss of xenon gas to the atmosphere: A key component of the proposed anesthesia gas, independent of any additional inhaled anesthetics or other gases that are present. The present lack of an accurate, reliable, and cost-effective xenon concentration sensor makes it very difficult to control the xenon concentration in the circuit and is a major obstacle to widespread use of xenon anesthesia. Phase I proves feasibility by (1) demonstrating the key aspects of the novel xenon gas sensor, and (2) producing a conceptual design for a closed-loop xenon anesthesia machine that will incorporate the xenon gas concentration sensor. PROPOSED COMMERCIAL APPLICATIONS: Xenon anesthesia is attractive for three broad applications: (1) xenon gas will potentially be the anesthetic agent of choice for a large fraction for the surgical procedures performed each year in the United States on patients with cardiovascular conditions; (2) because of fewer complications such as myocardial depression and rapid induction and emergence, xenon anesthesia can reduce the time patients spend in the hospital, with large benefits to health care costs; and (3) xenon can be used in combination with other anesthetics to reduce their concentration and consequently their side effects. The proposed research will lead to a practical device that will provide for the low-cost use of xenon as an anesthetic agent and enable widespread application of this anesthetic technique.